mirror of
https://github.com/michaelcmartin/Ophis.git
synced 2024-08-10 18:28:56 +00:00
272 lines
6.0 KiB
HTML
272 lines
6.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<HTML
|
|
><HEAD
|
|
><TITLE
|
|
>Preface</TITLE
|
|
><META
|
|
NAME="GENERATOR"
|
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
|
|
REL="HOME"
|
|
TITLE="Programming with Ophis"
|
|
HREF="book1.html"><LINK
|
|
REL="PREVIOUS"
|
|
TITLE="Programming with Ophis"
|
|
HREF="book1.html"><LINK
|
|
REL="NEXT"
|
|
TITLE="Getting a copy of Ophis"
|
|
HREF="x29.html"></HEAD
|
|
><BODY
|
|
CLASS="PREFACE"
|
|
BGCOLOR="#FFFFFF"
|
|
TEXT="#000000"
|
|
LINK="#0000FF"
|
|
VLINK="#840084"
|
|
ALINK="#0000FF"
|
|
><DIV
|
|
CLASS="NAVHEADER"
|
|
><TABLE
|
|
SUMMARY="Header navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TH
|
|
COLSPAN="3"
|
|
ALIGN="center"
|
|
>Programming with Ophis</TH
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="10%"
|
|
ALIGN="left"
|
|
VALIGN="bottom"
|
|
><A
|
|
HREF="book1.html"
|
|
ACCESSKEY="P"
|
|
><<< Previous</A
|
|
></TD
|
|
><TD
|
|
WIDTH="80%"
|
|
ALIGN="center"
|
|
VALIGN="bottom"
|
|
></TD
|
|
><TD
|
|
WIDTH="10%"
|
|
ALIGN="right"
|
|
VALIGN="bottom"
|
|
><A
|
|
HREF="x29.html"
|
|
ACCESSKEY="N"
|
|
>Next >>></A
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"></DIV
|
|
><DIV
|
|
CLASS="PREFACE"
|
|
><H1
|
|
><A
|
|
NAME="AEN10"
|
|
></A
|
|
>Preface</H1
|
|
><P
|
|
> Ophis is an assembler for the 6502 microprocessor - the famous
|
|
chip used in the vast majority of the classic 8-bit computers and
|
|
consoles. Its primary design goals are code readability and output
|
|
flexibility - Ophis has successfully been used to create programs
|
|
for the Nintendo Entertainment System, the Atari 2600, and the
|
|
Commodore 64.
|
|
</P
|
|
><P
|
|
> Ophis's syntax is noticably different from the formats
|
|
traditionally used for these chips; it draws its syntactic
|
|
inspiration primarily from the assemblers for more modern chips,
|
|
where the role of tokens is determined more by what they're made
|
|
of and their grammatical location on a line rather than their
|
|
absolute position on a line. It also borrows the sophisticated
|
|
methods of tracking the location of labels when writing relinkable
|
|
code—Ophis expects that the final output it produces will have
|
|
only a vague resemblance to the memory image when loaded. Most of
|
|
the alternatives when Ophis was first designed would place
|
|
instructions and data into a memory map and then dump that map.
|
|
</P
|
|
><P
|
|
> That said, there remain many actively used 6502 assemblers out
|
|
there. If you're already a seasoned 6502 assembly programmer, or
|
|
want to get your old sources built again, Ophis is likely not for
|
|
you—however, if you are writing new code, or are new to the
|
|
chip while still having other experience, then Ophis is a tool
|
|
built with you in mind.
|
|
</P
|
|
><DIV
|
|
CLASS="SECTION"
|
|
><H1
|
|
CLASS="SECTION"
|
|
><A
|
|
NAME="AEN15"
|
|
>History of the project</A
|
|
></H1
|
|
><P
|
|
> The Ophis project started on a lark back in 2001. My graduate
|
|
studies required me to learn Perl and Python, and I'd been
|
|
playing around with Commodore 64 emulators in my spare time, so
|
|
I decided to learn both languages by writing a simple
|
|
cross-assembler for the 6502 chip the C64 used in both.
|
|
</P
|
|
><P
|
|
> The Perl one—uncreatively
|
|
dubbed <SPAN
|
|
CLASS="QUOTE"
|
|
>"Perl65"</SPAN
|
|
>—was quickly abandoned, but
|
|
the Python one saw more work. When it came time to name it, one
|
|
of the things I had been hoping to do with the assembler was to
|
|
produce working Apple II programs. <SPAN
|
|
CLASS="QUOTE"
|
|
>"Ophis"</SPAN
|
|
> is
|
|
Greek for <SPAN
|
|
CLASS="QUOTE"
|
|
>"snake"</SPAN
|
|
>, and a number of traditions also
|
|
use it as the actual <I
|
|
CLASS="EMPHASIS"
|
|
>name</I
|
|
> of the serpent in
|
|
the Garden of Eden. So, Pythons, snakes, and stories involving
|
|
really old Apples all combined to name the
|
|
assembler.<A
|
|
NAME="AEN23"
|
|
HREF="#FTN.AEN23"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[1]</SPAN
|
|
></A
|
|
>
|
|
</P
|
|
><P
|
|
> Ophis slowly grew in scope and power over the years, and by 2005
|
|
was a very powerful, flexible macro assembler that saw more use
|
|
than I'd expect. In 2007 Ophis 1.0 was formally released.
|
|
However, Ophis was written for Python 2.1 and this became more
|
|
and more untenable as time has gone by. As I started receiving
|
|
patches for parts of Ophis, and as I used it for some projects
|
|
of my own, it became clear that Ophis needed to be modernized
|
|
and to become better able to interoperate with other
|
|
toolchains. It was this process that led to Ophis 2.
|
|
</P
|
|
><P
|
|
> This is an updated edition of <I
|
|
CLASS="EMPHASIS"
|
|
>Programming With
|
|
Ophis</I
|
|
>, including documentation for all new features
|
|
introduced and expanding the examples to include simple
|
|
demonstration programs for platforms besides the Commodore
|
|
64. It also includes updated versions of the <I
|
|
CLASS="EMPHASIS"
|
|
>To HLL
|
|
and Back</I
|
|
> essays I wrote using Ophis and Perl65 as
|
|
example languages.
|
|
</P
|
|
></DIV
|
|
></DIV
|
|
><H3
|
|
CLASS="FOOTNOTES"
|
|
>Notes</H3
|
|
><TABLE
|
|
BORDER="0"
|
|
CLASS="FOOTNOTES"
|
|
WIDTH="100%"
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="5%"
|
|
><A
|
|
NAME="FTN.AEN23"
|
|
HREF="f10.html#AEN23"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[1]</SPAN
|
|
></A
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="95%"
|
|
><P
|
|
>Ironically, cross-platform development
|
|
for the Apple II is extremely difficult, and while Ophis has
|
|
been very successfully used to develop code for the Commodore
|
|
64, Nintendo Entertainment System, and Atari 2600, it has yet to
|
|
actually be deployed on any of the Apples which inspired its
|
|
name.</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><DIV
|
|
CLASS="NAVFOOTER"
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"><TABLE
|
|
SUMMARY="Footer navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="book1.html"
|
|
ACCESSKEY="P"
|
|
><<< Previous</A
|
|
></TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="book1.html"
|
|
ACCESSKEY="H"
|
|
>Home</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="x29.html"
|
|
ACCESSKEY="N"
|
|
>Next >>></A
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
>Programming with Ophis</TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
> </TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
>Getting a copy of Ophis</TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></BODY
|
|
></HTML
|
|
> |